気泡離脱時における振動呼吸モードの可視化計測

抄録

Bubble oscillation in the breathing mode at the bubble release was investigated by flow visualization and image processing. The interface amplitude is usually a several micron meter with 1 kHz, so the direct observation is crucially difficult in the experiment. In this report, by means of direct optical observation with the special image processing, the interface displacement has been detected. With a Laplacian pyramid for the captured image group, decomposition, and frequency filtering, a target of fluctuations is able to extract in a sub-pixel order. We verify the method by Wu et al. (2012) and apply it to the breathing mode of bubbles The amplification procedure is as follows: 1) create a hierarchy of image at each time using the Laplacian pyramid method, 2) specify the frequency of the breathing mode, and apply a bandpass filter to each hierarchy, 3) multiply by the magnification and restore the image by overlaying each layer of the Laplacian pyramid, and 4) generate a new image at each time by overlaying the original image. After producing a calibration curve with a numerical simulation, the amplitude of the breathing mode is estimated.